When Demis Hassabis was 6 years old, he remembers his father giving him the age-old reassurance prompt used every day by millions of parents around the world—“do your best.” For a young Hassabis, already showing the precocious talents that were to culminate in his becoming one of the most important artificial intelligence leaders in the world, “do your best” opened up a whole host of possibilities.

“I’m a bit of an extreme person,” he said. “And I took it in a way [that’s] extreme and logical. I was sort of thinking: ‘What is your best? And how do I know I’ve done my best? It must mean to the point of complete exhaustion, just prior to near-death. Then you’ve done your best, have you? Isn’t that logical?’”

Hassabis was speaking at an event in London hosted by Intelligence Squared (there is a joke about Hassabis being “intelligence cubed”). Alongside him was Sebastian Mallaby, author of a new biography of Hassabis, The Infinity Machine. “AI is the most interesting transformation in the world, and Demis Hassabis is the most interesting figure in AI,” Mallaby said when asked, “Why now?” about the book.

“Doing his best”—to the point of exhaustion—has been a guiding mantra for Hassabis’s life. Interviewed by Fortune in February, the cofounder of Google DeepMind and Isomorphic Labs revealed that he has two workdays—daytime hours that most of us do, and a 10 p.m. to 4 a.m. shift to execute “side projects” and other smart ideas.

“Using all my chess training [Hassabis was a recognized master-level chess player by the age of 13], that’s the way I think about life. In a very considered way, planning back from your goal, breaking that down into sub-goals. I think it’s generally applicable to life, or at least that’s what I’ve tried to do, and it’s been pretty effective.”

Being effective while based not in the global home of AI innovation—Silicon Valley—but in London, has raised eyebrows. Surely, after DeepMind was bought by Google in 2014, a move to Mountain View would have been a natural next step?

Not for Hassabis, who has argued that there needs to be more than one center of thinking in the world if we are to correctly balance the risks and opportunities of AI.

“There’s a bit of an underdog in me,” he said. “I wanted to show that I’m passionate about the U.K. and that London and the U.K. could do this. But the main thing was: I knew there was the talent here.

“I knew we would have the field to ourselves for about four or five years, the formative years of DeepMind, and we had this incredible talent that was being overlooked in the U.S.

“And with the success of DeepMind and a few other companies here, it’s shown that deep tech can be viable outside of Silicon Valley. Of course, the U.S. giants have realized this, both the VCs and the big tech companies, and they’ve invested now—many of them have their European head offices here in the U.K. and in London.”

In 2010, when DeepMind was founded, Hassabis was already convinced that AI would be the transformative technology it has turned out to be.

“We planned for success even back in 2010, which seems crazy, because nothing was working,” he said. “[But that’s] how it’s turned out. And the people that are making it shouldn’t just be from 20 square miles of the U.S. It’s going to affect the entire globe. So, I think a global perspective on AI, what it should be used for, how it should be deployed, the ethics of it, the technology itself, [is important].

“We contribute to that by having a big base here and thousands of researchers, and we’ve just opened a beautiful new office just around the corner as part of making that conversation global, even within Google, and hopefully for the whole field.”

Although Hassabis has said he likes nothing better than a commercial battle (when ChatGPT launched ahead of Google Gemini his response was, “This is war”), he is more motivated by the scientific discovery aspects of artificial intelligence. “Solving disease” and the climate crisis are, he believes, fundamental challenges AI can tackle.

There is also the issue of safety, particularly with the approach of the next level of AI: artificial general intelligence. “At the back of my mind, I’ve got this gnawing feeling that there’s something much more important, much bigger than the commercial race, which is getting AGI safely over the line for humanity and to make sure that the benefits fully outweigh the risks.

“And, you know, I’m going to try. We’re only one actor in this now; there’s five or six [other] leaders, and there’s China as well, and the Chinese labs. And so I think in the next few years, the story is still to be written on how this is going to go.

“There needs to be more cooperation and coordination at an international level, ideally—although that’s very hard with geopolitics as it is today—around safety topics and debates around the benefits versus the risks.”

Mallaby is asked at the end of the hour-long discussion whether the world can trust Hassabis with such a gargantuan task.

“I think I can say with pretty good authority—having not only talked to him for more than 30 hours but also talking to 100 other people around Demis, including bumping into old friends of mine who had kids at the same school as Demis’s kids—I really do know the person next to me extremely well. And I’m very confident in saying that his values are good. He wants this—first of all, for AI to be good for society. And secondly, his primary motivation is scientific discovery. And that’s what he’s dreamt of from the beginning. That is who he is.”